APDM is a young company focused on developing and commercializing professional systems using wearable inertial sensors for monitoring of human movement and movement disorders. In Phase I, we developed the novel, Instrumented Stand and Walk test (ISAW) using APDM's proprietary, Opal movement monitors and Mobility Lab system. We validated the ISAW by demonstrating that the ISAW measures were sensitive to severity of Parkinson's disease (PD) and levodopa treatment. The ISAW allows clinicians and nonexperts to quickly obtain objective measures of standing balance, step-initiation, gait, and turning. The ultimate goal for the product is to provide a quick, portable, clinical system to quickly and automatically obtain objective measures of balance and gait disorders to predict fall risk using body-worn sensors. This Phase II STTR proposal will expand the use of the ISAW from PD to elderly fallers. We will partner with the largest, longitudinal study of falls in elderl men, the Osteoporotic Fractures in Men Study (MrOS), to characterize balance and gait in 361 community-dwelling older men, and with the Oregon Center of Aging and Technology (ORCATECH) in 97 community-dwelling older women. This proposal will not only demonstrate the feasibility and usefulness of the ISAW to quickly quantify balance and gait for multicenter clinical trials, it will also develop a unique Fall Risk Report and provide the ISAW with normative values for the elderly. This 3-year study will have both a Clinical Research and a Technology Development Aim to prepare the ISAW to expand market penetration from research to clinical practice as an objective biomarker for fall risk and mobility disability. The impact of the ISAW wil be on clinicians interested in measuring fall risk in the elderly, including primary care physician, neurologists, geriatricians, rehabilitation professionals, assisted living facilities, hospitals an athletic trainers. The Specific Aims are: Aim I. Clinical Research: Develop a fall risk evaluation system for clinicians from the ISAW test (Milestone 1. Develop a Fall Risk Report and Milestone 2. Develop reference values for integrity of balance and gait across older ages). Aim II. Technology Development: Prepare the ISAW to be practical and attractive for clinical practice as well as clinical trials (Milestone 3. Mobility Exchange: Prepare data repository for multi-site clinical data collection from the ISAW test (Milestone 4. Mobility Clinic: Simplify user-interface and reporting for clinicians, and Milestone 5. FDA: Put quality systems and regulatory compliance in place so ISAW can be marketed for clinical practice). This Phase II proposal will transform APDM's ISAW protocol into the first technological system for clinicians (Mobility Clinic) and clinical researchers (Mobility Lab) to provide a validated, objective fall risk evaluation, as well as comprehensive balance and gait disorder assessment.